An exoergic resin composition, an exoergic grease, and an exoergic coating composition are used for electrical products which are required to inhibit built-up heat. These are obtained by mixing an inorganic particle having high heat-conductivity as an exoergic filler with resins, oils and so on. It has been investigated that the exoergic filler which is used for such purpose is converted to a highly heat-conductive composition for high exoergic property.
As the exoergic filler, various high heat-conductive fillers such as alumina, boron nitride, aluminum nitride, zinc oxide, and magnesium oxide are known (PATENT DOCUMENTS 1 and 2). Recently, a method for increasing the filling rate of the exoergic material in a composition by combining various particles having different particle diameter is performed (PATENT DOCUMENTS 3 AND 4).
As mentioned above, it is known to increase the exoergic property by combining two or more kinds of particles having different particle diameter. There is no attempt to increase the exoergic property by combining some particles having unique particle shape.
On the other hand, a needle-shaped zinc oxide having needle shape is known (PATENT DOCUMENT 5). There is no attempt to use the zinc oxide in combination with other exoergic fillers.